/*
 * InputElement.java July 2006
 *
 * Copyright (C) 2006, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package wx.xml.simpleframework.xml.stream;

import wx.xml.stax.api.stream.Location;

/**
 * The <code>InputElement</code> represents a self contained element
 * that will allow access to its child elements. If the next element
 * read from the <code>NodeReader</code> is not a child then this
 * will return null. The input element node also allows the attribute
 * values associated with the node to be accessed.
 *
 * @author Niall Gallagher
 * @see wx.xml.simpleframework.xml.stream.NodeReader
 */
class InputElement implements InputNode {

    /**
     * This contains all the attributes associated with the element.
     */
    private final InputNodeMap map;

    /**
     * This is the node reader that reads from the XML document.
     */
    private final NodeReader reader;

    /**
     * This is the parent node for this XML input element node.
     */
    private final InputNode parent;

    /**
     * This is the XML element that this node provides access to.
     */
    private final EventNode node;

    /**
     * Constructor for the <code>InputElement</code> object. This
     * is used to create an input node that will provide access to
     * an XML element. All attributes associated with the element
     * given are extracted and exposed via the attribute node map.
     *
     * @param parent this is the parent XML element for this
     * @param reader this is the reader used to read XML elements
     * @param node   this is the XML element wrapped by this node
     */
    public InputElement(InputNode parent, NodeReader reader, EventNode node) {
        this.map = new InputNodeMap(this, node);
        this.reader = reader;
        this.parent = parent;
        this.node = node;
    }

    /**
     * This is used to return the source object for this node. This
     * is used primarily as a means to determine which XML provider
     * is parsing the source document and producing the nodes. It
     * is useful to be able to determine the XML provider like this.
     *
     * @return this returns the source of this input node
     */
    @Override
    public Object getSource() {
        return node.getSource();
    }

    /**
     * This is used to acquire the <code>Node</code> that is the
     * parent of this node. This will return the node that is
     * the direct parent of this node and allows for siblings to
     * make use of nodes with their parents if required.
     *
     * @return this returns the parent node for this node
     */
    @Override
    public InputNode getParent() {
        return parent;
    }

    /**
     * This provides the position of this node within the document.
     * This allows the user of this node to report problems with
     * the location within the document, allowing the XML to be
     * debugged if it does not match the class schema.
     *
     * @return this returns the position of the XML read cursor
     */
    @Override
    public Location getLocation() {
        return reader.getLocation();
    }

    /**
     * Returns the name of the node that this represents. This is
     * an immutable property and should not change for any node.
     * This provides the name without the name space part.
     *
     * @return returns the name of the node that this represents
     */
    @Override
    public String getName() {
        return node.getName();
    }

    /**
     * This is used to acquire the namespace prefix for the node.
     * If there is no namespace prefix for the node then this will
     * return null. Acquiring the prefix enables the qualification
     * of the node to be determined. It also allows nodes to be
     * grouped by its prefix and allows group operations.
     *
     * @return this returns the prefix associated with this node
     */
    public String getPrefix() {
        return node.getPrefix();
    }

    /**
     * This allows the namespace reference URI to be determined.
     * A reference is a globally unique string that allows the
     * node to be identified. Typically the reference will be a URI
     * but it can be any unique string used to identify the node.
     * This allows the node to be identified within the namespace.
     *
     * @return this returns the associated namespace reference URI
     */
    @Override
    public String getReference() {
        return node.getReference();
    }

    /**
     * This method is used to determine if this node is the root
     * node for the XML document. The root node is the first node
     * in the document and has no sibling nodes. This is false
     * if the node has a parent node or a sibling node.
     *
     * @return true if this is the root node within the document
     */
    @Override
    public boolean isRoot() {
        return reader.isRoot(this);
    }

    /**
     * This is used to determine if this node is an element. This
     * allows users of the framework to make a distinction between
     * nodes that represent attributes and nodes that represent
     * elements. This is particularly useful given that attribute
     * nodes do not maintain a node map of attributes.
     *
     * @return this returns true as this instance is an element
     */
    @Override
    public boolean isElement() {
        return true;
    }

    /**
     * Provides an attribute from the element represented. If an
     * attribute for the specified name does not exist within the
     * element represented then this method will return null.
     *
     * @param name this is the name of the attribute to retrieve
     * @return this returns the value for the named attribute
     */
    public InputNode getAttribute(String name) {
        return map.get(name);
    }

    /**
     * This returns a map of the attributes contained within the
     * element. If no elements exist within the element then this
     * returns an empty map.
     *
     * @return this returns a map of attributes for the element
     */
    @Override
    public NodeMap<InputNode> getAttributes() {
        return map;
    }

    /**
     * Returns the value for the node that this represents. This
     * is an immutable value for the node and cannot be changed.
     * If there is a problem reading an exception is thrown.
     *
     * @return the name of the value for this node instance
     */
    public String getValue() throws Exception {
        return reader.readValue(this);
    }

    /**
     * The method is used to acquire the next child attribute of this
     * element. If the next element from the <code>NodeReader</code>
     * is not a child node to the element that this represents then
     * this will return null, which ensures each element represents
     * a self contained collection of child nodes.
     *
     * @return this returns the next child element of this node
     * @throws Exception thrown if there is a problem reading
     */
    @Override
    public InputNode getNext() throws Exception {
        return reader.readElement(this);
    }

    /**
     * The method is used to acquire the next child attribute of this
     * element. If the next element from the <code>NodeReader</code>
     * is not a child node to the element that this represents then
     * this will return null, also if the next element does not match
     * the specified name then this will return null.
     *
     * @param name this is the name expected fromt he next element
     * @return this returns the next child element of this node
     * @throws Exception thrown if there is a problem reading
     */
    @Override
    public InputNode getNext(String name) throws Exception {
        return reader.readElement(this, name);
    }

    /**
     * This method is used to skip all child elements from this
     * element. This allows elements to be effectively skipped such
     * that when parsing a document if an element is not required
     * then that element can be completely removed from the XML.
     *
     * @throws Exception thrown if there was a parse error
     */
    @Override
    public void skip() throws Exception {
        reader.skipElement(this);
    }

    /**
     * This is used to determine if this input node is empty. An
     * empty node is one with no attributes or children. This can
     * be used to determine if a given node represents an empty
     * entity, with which no extra data can be extracted.
     *
     * @return this returns true if the node is an empty element
     * @throws Exception thrown if there was a parse error
     */
    public boolean isEmpty() throws Exception {
        if (!map.isEmpty()) {
            return false;
        }
        return reader.isEmpty(this);
    }

    /**
     * This is the string representation of the element. It is
     * used for debugging purposes. When evaluating the element
     * the to string can be used to print out the element name.
     *
     * @return this returns a text description of the element
     */
    public String toString() {
        return String.format("element %s", getName());
    }

    @Override
    public String debugDescription() {
        return String.format("<%s %s>", getName(), map.debugDescription());
    }
}


